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This is intentional and was added in 4.0.7 to help people understand the tradeoffs. Flight height, overlap, altitude and imaging rate are all related. If you adjust one it may force the adjustment of others.
You can buy a little extra by using a super fast SD card and adjusting the SD card write speed in the Settings to 2 seconds/frame. Or slow down the maximum flight speed.
You can have a ton of overlap or flow low but unless you have a super fast camera you cannot have both.